Gravity Probe B

Testing Einstein's Universe

Special & General Relativity Questions and Answers

How do you really know that the limits to general relativity for strong
fields are set inside black holes?

Because general relativity is a classical field theory which predicts
that under certain conditions, infinities will occur...called singularities.
All known singularities in the theory seem to be hidden behind event horizons.
At these locations, space-time curvature defined by the magnitude of the
so-called Riemann Tensor, goes to infinity as the radius of the system goes to
zero. It is expected that a make-over of general relativity by a fully quantum
mechanical field theory will remove these singularities and replace them by
some as yet undefined quantum condition, such as the finite graininess
of space-time itself at the Planck Scale.